1. Statement of the Technical Field
The inventive arrangements relate generally to inductors and more particularly to toroidal inductors.
2. Description of the Related Art
Embedded toroidal inductors are known in the art. For example, U.S. Pat. No. 6,990,729 to Pleskach et al. discloses a method for forming an embedded toroidal inductor. The method includes the step of forming in a ceramic substrate a first plurality of conductive vias radially spaced a first distance from a central axis so as to define an inner circumference. A second plurality of conductive vias is formed radially spaced a second distance about the central axis so as to define an outer circumference. A first plurality of conductive traces forming an electrical connection between substantially adjacent ones of the first and second plurality of conductive vias is formed on a first surface of the ceramic substrate. Further, a second plurality of conductive traces forming an electrical connection between circumferentially offset ones of the first and second plurality of conductive vias is formed on a second surface of the ceramic substrate opposed from the first surface to define a three dimensional toroidal coil.
In conventional embedded inductor designs of the prior art, there are two components that comprise the toroidal inductor coil conductive traces and conductive vias. Of these two components, the conductive traces account for the vast majority of the direct current resistance (DCR) due to their very small cross sectional area in comparison to the conductive vias. DCR is defined as the resistance of the inductor winding as measured using direct current. Notably, an increase in the value of DCR will cause a decrease in the quality factor (Q) of the inductor.
Since Q is a measure of the relative losses in an inductor, the higher the DCR the lower the Q in the system. In many applications, it is desirable to provide an inductor with very high Q. Therefore, what is needed is an improved toroidal inductor design that can reduce the direct current resistance of the inductor and thereby increase Q. At the same time, the design should not increase the x-y plane size of the toroidal footprint or require any additional machining or post processing steps.